艾比湖滨岸盐碱土中碳酸盐的XRD衍射特征与微观形态分析

XRD Diffraction Characteristics and Microscopic Morphology of Carbonates in Saline-Alkaline Soil from the Shore of the Aibi Lake

结合X射线衍射(XRD)、扫描电镜(SEM)和能谱分析(EDS)方法,对现代盐湖沉积环境下,新疆艾比湖滨岸盐碱土中碳酸盐的分布特征、存在形式以及与其他土壤原生、次生矿物之间的关系进行探讨,结果表明:艾比湖滨岸盐碱土中的原生矿物主要是石英和长石,粘土矿物主要为绿泥石和伊利石,土壤矿物的风化程度顺序为北部>西部>东部,西部样点的现代盐湖化学沉积作用最为显著,北部样点则生物风化过程十分强烈;XRD方法和气量法分别测得的碳酸盐含量之间呈极显著正相关关系,判定系数R^2达0.640 9。当盐碱土中含有较高的绿泥石时,碳汇潜力会增加,同时,XRD方法对碳酸盐相对含量的鉴定误差也明显增加,衍射峰形变得复杂,碳酸盐含量明显被低估,低估原因可能与有机质含量高导致的弥散散射增加及粘土矿物含量高使得类质同象现象增加有关;西部和北部土壤矿物溶蚀强烈,石膏以纤维状或长柱状晶体分散或放射状分布于方解石晶体之间,方解石则以异质成核形式呈颗粒状或片状在其他矿物或底质表面生长,表现为次生碳酸盐形貌特征。

Based on the XRD ,SEM and EDS methods ,this paper discovers the distribution and forms of carbonate in saline-al-kaline soils from the shore of The Abi Lake in Xinjiang ,under the depositional environment of modern salt lake .The results showed that the primary minerals in the saline soil are mainly quartz and feldspar ,and the clay minerals are mainly chlorite and illite .The order of weathering of soil minerals is ：north＆gt;western＆gt;eastern .west sample of modern salt lake chemical deposition is the most significant ,northern sample is very strong biological weathering process .XRD method and volume method respec-tively measured were very significant positive correlation between carbonate content ,determination coefficient R2 is 0.6409 . When the salinity soil contains more chlorite ,the potential of carbon sink can be significantly improved .Meanwhile ,the identifi-cation error of carbonate relative content by XRD method is increased and the shape of diffraction peak becomes complex ,which results in an obvious underestimation of the carbonate content .underestimate the reason may be related to diffuse scattering caused by high organic matter content increased and high clay mineral content makes mass is associated with increased with iso-morphism phenomena .The soils from western and northern areas were severely eroded ,and the gypsum is dispersed or radially distributed between the calcite crystals in the form of fibrous or long columnar crystals .The calcite is in the form of heterogene-ous nucleation or in the form of granules or flakes on the surface of other minerals or substrates ,which indicates the characteris-tics of secondary carbonate morphology .